Photoresist-forming compositions

ABSTRACT

A PHOTORESIST-FORMING COMPOSITION COMPRSISING A PHOTO ACTIVATOR HAVING A POLYCHLORINATED OR POLYBROMINATED METHYL GROUP CAPABLE OF FORMING A FREE RADICAL BY THE ACTION OF LIGHT AND A HOMOPOLYMER OR A CO-POLYMER WITH OTHER VINYL MONOMER, OF A MONOMER REPRESENTED BY THE GENERAL FORMULA   -CH(-A)-C(-R1)(-X-N(-R2)-(2-R3-1,3-PHENYLENE)-R4)- OR   -CH2-C(-R1)(-N(-R2)-(2-R3-1,3-PHENYLENE)-R4)-   WHEREIN A IS A HYDROGEN ATOM, A CARBOXYLIC ACID OR CARBOXYLIIC ACID AMIDE; X IS-COOCH2CH2-,   -CONHCH2CH2-   -COSCH2CH2, -CONH-, -CH2-, -OSO2NH-, -OSO2OO-, -CONHO-; R1 IS A HYDROGEN ATOM OR A LOWER ALKYL GROUP: R1 HYDROGEN ATOM, A LOWER ALKYL GROUP OR A SUBSTITUTED OR UNSUBSTITUTED PHENYL GROUP; AND R3 AND R4 ARE INDIVIDUALLY A HYDROGEN ATOM OR A LOWER ALKYL GROUP, PROVIDED THAT IN THE CASE OF THE FORMULA II, R2 AND R3 MAY FORM A HETEROCYCLIC RING TOGETHER WITH NITROGEN AND THE BENZENE RING, AND R3 AND R4 MAY FORM A NAPHTHALENE RING TOGETHER WITH THE BENZENE RING.

U ited States Pate t Ofice 3,579,343 Patented May 18, 1971 3,579,343 PHOTORESIST-FORMING COMPOSITIONS Motoo Kogure and Shoichiro Hoshino, Tokyo, Japan, assignors to Konishiroku Photo Industry Co., Ltd.

No Drawing. Filed Apr. 16, 1968, Ser. No. 721,621 Claims priority, application Japan, Apr. 25, 1967, 42/25,988 Int. Cl. G03c 1 70, 1/72 US. Cl. 9690R 2 Claims ABSTRACT OF THE DISCLOSURE A photoresist-forming composition comprising a photo activator having a polychlorinated or polybrominated methyl group capable of forming a free radical by the action of light and a homopolymer or a co-polymer with other vinyl monomer, of a monomer represented by the general formula wherein A is a hydrogen atom, a carboxylic acid or carboxylic acid amide; X is COOCH CH This invention relates to a novel photoresist-forming composition comprising a polymer and a photo-activator having a polyhalogeriated methyl group capable of forming a free radical by action of light. When the present composition is irradiated with light, the polymer is crosslinked to cause photo-curing, and when the composition is subjected to developing treatment, a relief image, which can be utilized for offset, relief or gravure printing, is formed.

A conventional light-sensitive compositions using polymers, there have been known those in which gelatine or polyvinyl alcohol and a bichromate are used in combination, and those in which a polymer and a diazo compound are used in combination. Further, light-sensitive compositions which contain polyvinyl cinnamate so as to utilize the photodimerization of the cinnamate group also have been known. These conventional light-sensitive compositions, however, have such drawbacks that even when they are exposed to light through negatives, image portions cannot be discriminated from non-image portions, unless they are treated with a developer to form relief images. Even if the above compositions are subjected to such treatment, the resulting images are diflicultly distinguished in detailed portions, and therefore there has been adopted such a process that a coloring agent has previously been incorporated into the light-sensitive compositions. This process, however, necessarily results in decrease of photographic speed and has required long time exposure. Further, there has been known a process in which relief images are dyed after developing treatment. This process has, however, required such double operations as developing treatment and dyeing treatment. Thus,

n the conventional light-sensitive compositions using poly mers have had such drawback that, in order to obtain visible images, they should necessarily be subjected to developing and dyeing treatment steps. Accordingly, when said compositions have been left merely in an exposed state without any further treatment, exposed portions have not been able to be discriminated from unexposed portions to bring about much fear of double exposure.

The light-sensitive compositions of the present invention are novel compositions which have overcome all the above-mentioned drawbacks. When the present compositions are exposed to light, polymers contained therein are cross-linked imagewise, with dye formation, to give faintly colored images, and when they are subjected to developing treatment, the exposed portions are clearly developed in deep color, with removal of unexposed portions, thereby to form visible relief images.

The polymers employed in the present invention are homopolymers, or copolymers with other vinyl monomers, of monomers represented by the general formula wherein A is a hydrogen atom, or a carboxylic acid or carboxylic acid amide group; X is a group capable of connecting the carbon in the main chain with an amino group which has substituted the aromatic ring; R is a hydrogen atom or a lower alkyl group; R is a hydrogen atom, a lower alkyl group or a substituted or unsubstituted phenyl group; and R and R are individually a hydrogen atom or a lower alkyl group, provided that in the case of Formula II, R and R may form a heterocyclic ring together with nitrogen and the benzene ring, and R and R may form a naphthalene ring together with the benzene ring.

Usable as the vinyl monomers are any of such monomers as styrene, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, itaconic acid, methyl acrylate, .ethyl acrylate, butyl acrylate, methyl methacrylate, methyl achloro-acrylate, ethyl a-chloroacrylate, ethyl methacrylate, ethyl ethacrylate, maleic anhydride, vinylidene chloride, and the like.

Typical examples of these polymers are as shown below, but polymers usable in the present invention are not limited thereto.

( C Hz CODE 50 CH3 CH1 OOH Synthesis examples of the polymers employed in the present invention are set forth below.

SYNTHESIS EXAMPLE 1 Synthesis of exemplified polymer (1) 1 mole of N-ethyl-N-phenylamino-ethanol is dissolved in 500 cc. of pyridine, and the solution is cooled to C. To the solution, 1 mole of methacrylic acid chloride is gradually added dropwise with stirring. After the dropwise addition, the reaction liquid is stirred at room temperature for 2-3 hours and is then charged into a large amount of ice water. The resulting oily substance is extracted with ether and is washed with water until its pyridine odor has been removed. The thus formed ether solution is dried with anhydrous sodium sulfate and then added with a small amount of hydroquinone. Subsequently, the ether is vaporized off and the reaction liquid liquid is then subjected to reduce pressure distillation at 135 C. and 4 mm. Hg to obtain N-ethyl-N-phenylaminoethyl methacrylate. 1 g. of the N-ethyl-N-phenylaminoethyl methacrylate is dissolved in cc. of methyl ethyl ketone. The solution is charged wifll 5 mg. of a,ot'- azo-bis-isobutyronitrile and is then heated at 60 C. for 5 hours to obtain a polymer solution. This reaction liquid is poured into ether, whereby a white polymer is precipitated.

SYNTHESIS EXAMPLE 2 Synthesis of exemplified polymer (4) 1 mole of N-ethyl-N-phenylaminoethyl amine is dissolved in 620 cc. of pyridine. To the solution, 1 mole of methacryl chloride is gradually added dropwise at 0- 10 C. After the dropwise addition, the mixture is stirred I for 8 hours. After completion of the reaction, pyridine hydrochloride is separated by filteration, and the reaction liquid is poured into ice water. Thereafter, the resulting precipitate is thoroughly washed with water to obtain N-ethyl-N-phenylaminoethyl rnethacrylamide in the form of white crystalline needles. 1.1 g. of the thus obtained N-ethyl-N-phenylaminoethyl rnethacrylamide and 0.5 g. of styrene are dissolved in 10 cc. of methyl ethyl ketone. The solution is charged with 5 mg. of 11,01.- azo-bis-isobutyronitrile and is then heated at 70 C. for 12 hours. Subsequently, the solution is charged into a large amount of methanol to obtain a white polymer.

The photoactivators employed in the present invention, i.e. photoactivators having a polyhalogenated methyl group capable of forming a free radical by action of light, are compounds represented by the general formula R4- S Oz-CXaRa,

wherein R is a hydrogen atom, an alkyl group, an aryl group, a halogen atom or a heterocyclic ring; R is a hydrogen or halogen atom; R is a common substituent such as a nitro group, a halogen atom or an alkyl group; R is an alkyl group, an aryl group or a heterocyclic ring; and X is a chlorine or bromine atom.

The halogen-containing compounds represented by the above-mentioned general formulas include, for example,

2,2,2 tribromoethanol, p-nitro a,a,a-tribromoacetophenone, w,w,w-tribromoquinalidine, 2-w,w,w-tribromomethyl- S-nitroquinoline, 2-w,w,w-trichloromethyl-6-nitrobenzothiazole, a,w,w-dibromomethyl-4-chloropyridine, hexabromodimethyl sulfoxide, tribromomethyl-phenyl sulfone, 4-nitrotribromomethyl-phenyl sulfone, and 2-tribromomethylsulfonyl benzothiazole.

The light-sensitive compositions of the present invention are composed of the above-mentioned specific polymers and photoactivators. In actual use, the present composition is dissolved in an organic solvent, and the solution is coated onto such a support as aluminum plate, zinc plate, copper plate, plastic film or sheet, or paper, and is then dried. 'Preferable as the organic solvent is ethanol, acetone, dioxane or methyl Cellosolve. The coating liquid composition of the present invention is preferably 1-50 parts of polymer and 0.1-50 parts of photoactivator per parts by weight of solvent. However, the proportions of polymer and photoactivator may be greater or smaller than said proportions.

The polymer employed in the present invention has, in the aromatic ring, an active hydrogen in the paraposition to the amino group which has substituted the aromatic ring positioned on the side chain of the polymer. On the other hand, the photoactivator, which is a compound having a polyhalogenated methyl group, is such that when it is irradiated with light, the polyhalogenated methyl group yields a carbon free radical. Accordingly, when the present composition, in which said polymer and photoactivator are present together, is exposed to light, the polyhalogenated methyl group of the photoactivator is connected through a carbon-carbon to the active hydrogen-bearing carbon in the para-position to the amino group of the aromatic ring in the side chain of the polymer. As the result, the polymer and the photoactivator are successively cross-linked with dye formation to give a faintly colored image. When the exposed material is treated with a solvent capable of dissolving the polymer, the exposed portion which is now composed of the crosslinked polymer in the form of a high molecular weight dye of the diphenylmethane or triphenylmethane type remains intact while the unexposed portion is removed olf, whereby a visible relief image is obtained.

The novel photoresist-forming compositions of the present invention can also be color sensitized. That is, when the compounds having polyhalogenated methyl groups are incorporated with acridine dye, merocyanine dye or styryl dye, the compositions can be greatly improved in sensitivity.

The present compositions are free from dark reaction and, when the compositions are exposed to light through negatives, exposed portions which give faintly colored images greatly differ in solvent solubility from unexposed portions. Accordingly, when the compositions after exposure are treated with solvents capable of dissolving the polymers contained therein, visible relief images can be obtained without necessitating a dyeing step. The thus obtained relief images are stable against etching liquids, so that they can be used for metal etch resist, offset printing, relief printing, etc.

The present invention is illustrated in further detail below with reference to examples.

EXAMPLE 1 0.5 g. of p-nitro-tribromomethyl-phenyl sulfone and 0.7 g. of a 1:1 copolymer of styrene and N-ethyl-N- phenylaminoethyl acrylamide are dissolved in 10 cc. of methyl ethyl ketone, and the solution is coated onto an aluminum plate and is then dried. On the thus treated aluminum plate, a negative is placed, and the composite is subjected to a vacuum printer and is exposed for 10 minutes to a 500 w. tungsten lamp to form a pale blue positive image. When this aluminum plate is rubbed with absorbent cotton impregnated with dioxane, unexposed portion is dissolved and removed to leave a deep blue positive relief image on the aluminum plate. This image is useful as a name plate or the like.

EXAMPLE 2 g. of poly (N-phenyl-N-acryloyl hydrazine) and 5 g. of hexabromodimethyl sulfone are dissolved in 80 cc. of dioxane, and the solution is coated onto a grained aluminum plate. Through a microfilm negative, this lightsensitive plate is exposed to light for minutes by means of an enlarging printer. Subsequently, the plate is lightly rubbed with absorbent cotton impregnated with dioxane, whereby unexposed portion is removed to leave a pink positive image. This image is thoroughly washed with water and is then treated with damping water. When this image is subjected to an offset printing machine, more than 1000 copies excellent in image reproduction can be obtained.

EXAMPLE 3 6 g. of 2-tribromomethylsulfonyl benzothiazole and 6 g. of a 4:6 copolymer (M.W. about 150,000) of N-ethyl- N-phenylamino ethyl methacrylate and methacrylic acid are dissolved in 100 cc. of dioxane. The solution is coated by means of a whirler onto a polished zinc plate and is then dried. Through a negative, the zinc plate is exposed by means of a fluorescent lamp, vacuum printer, whereby a pale blue positive image is obtained. When the image is developed with a 0.05% aqueous caustic soda solution, unexposed portion is removed and the image portion becomes deep blue. The plate is etched with a Dow etching liquid and is subjected, after water-washing, to a relief printing machine to obtain many clear copies.

EXAMPLE 4 5 g. of 2-w,w,w-tribromomethylquinoline and 5 g. of a vinylmethylether-maleic acid half-p-anilinophenylamide copolymer are dissolved in 100 cc. of methylethylketone. The solution is sprayed onto an iron plate coated with a white primer and is then dried. Through a negative, the iron plate is exposed to light by means of a drafting enlarger, whereby a brown image is formed on the white iron plate. This image can withstand flame cutting.

What is claimed is:

1. A photoresist-forming composition which comprises a photoactivator having a polychlorinated or polybrominated methyl group capable of forming a free radical by action of light and a homopolymer, or a copolymer with other vinyl monomer, of a monomer represented by the general formula wherein A is a hydrogen atom, a carboxylic acid or carboxylic acid amide group; X is COOCH CH R is a hydrogen atom or a lower alkyl group; R is a hydrogen atom, a lower alkyl group or a substituted or unsubstituted phenyl group; and R and R are individual ly a hydrogen atom or a lower alkyl group, provided that in the case of the Formula II, R and R may form a heterocyclic ring together with nitrogen and the benzene ring, and R and R may form a naphthalene ring together with the benzene ring.

2. A photoresist-forming composition as claimed in claim 1, wherein said copolymer is the copolymerization product of the monomer represented by the general Formula I or II with a vinyl monomer selected from styrene, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, itaconic acid, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, methyl a-chloro-acrylate, ethyl rx-ChlOIO-3CI'Ylflt6, ethyl methacrylate, ethyl ethacrylate, maleic anhydride and vinylidene chloride.

References Cited UNITED STATES PATENTS 1,820,593 8/1931 Beebe 96-115X 3,056,673 10/1962 Wainer 96--115X 3,147,117 9/1964 Wainer et a1 96-115X 3,201,240 8/1965 Faber 96-115X 3,268,333 8/1966 Allman et a1 96115X 3,443,945 5/1969 Fichter 96115X RONALD H. SMITH, Primary Examiner US. Cl. X.R. 96115R 

